JP3612929B2 - OSCILLATOR CIRCUIT, ELECTRONIC CIRCUIT USING THE SAME, SEMICONDUCTOR DEVICE USING THEM, ELECTRONIC DEVICE, AND WATCH - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an oscillation circuit, an electronic circuit using the same, a semiconductor device using the same, an electronic apparatus, and a timepiece.
[0002]
[Background Art and Problems to be Solved by the Invention]
Conventionally, an oscillation circuit using a crystal resonator has been widely used in portable wristwatches, portable telephones, computer terminals, and the like. In such portable electronic devices, it is necessary to save power consumption and extend the life of the battery.
[0003]
The crystal oscillation circuit includes a signal inverting amplifier and a feedback circuit including a crystal resonator. The signal inverting amplifier includes a pair of transistors, and each transistor has, for example, a gate used as an input side and a drain used as an output side. In this case, the drain sides of the transistors are connected to each other, and the source sides thereof are connected to the ground and the power supply voltage side, respectively.
[0004]
In the crystal oscillation circuit having the above configuration, when a power supply voltage is applied to the signal inverting amplifier, the output of the signal inverting amplifier is phase-inverted 180 degrees and fed back to the gates of the transistors. By this feedback operation, the transistors constituting the signal inverting amplifier are alternately turned on and off, the oscillation output of the crystal oscillation circuit gradually increases, and finally the vibrator starts to vibrate stably.
[0005]
However, in the conventional crystal oscillation circuit, the absolute value of the voltage Vreg applied to the signal inverting amplifier is set to be equal to or greater than the sum of the absolute values of the threshold voltages VTP and VTN of each transistor as shown in the following equation.
[0006]
| Vreg |> | VTP | + | VTN | (1)
The present inventor has found that this causes the short current Is to flow from the high potential side to the low potential side in the signal inverting amplifier, which is a problem in reducing the power consumption of the entire circuit.
[0007]
An object of the present invention is to provide an oscillation circuit capable of reducing short-circuit current flowing in a signal inverting amplifier and oscillating with low power consumption, an electronic circuit using the oscillation circuit, a semiconductor device using the same, an electronic apparatus, and a timepiece. There is.
[0008]
[Means for Solving the Problems]
(1) In order to achieve the above object, the present invention provides:
A first semiconductor switching element constituting a signal inverting amplifier;
The sum of the absolute values of the threshold voltages of the second semiconductor switching elements is set to a value equal to or greater than the absolute value of the power supply voltage of the signal inverting amplifier to limit a short current flowing through the signal inverting amplifier.
[0009]
(2) The present invention also provides:
A signal inverting amplifier;
A feedback circuit that has a crystal resonator connected between the output side and the input side of the signal inverting amplifier, inverts the phase of the output signal of the signal inverting amplifier, and inputs the feedback to the signal inverting amplifier;
Including
The signal inverting amplifier is:
A first circuit including a first semiconductor switching element connected to a first potential side and driven to be turned on / off by the feedback input to drive the crystal resonator;
A second semiconductor switching element connected to a second potential side different from the first potential and driven on and off at a timing different from that of the first semiconductor switching element by the feedback input to drive the crystal resonator to be excited; A second circuit;
Including
The sum of the absolute values of the threshold voltages of the first semiconductor switching element and the second semiconductor switching element constituting the signal inverting amplifier is equal to or greater than the absolute value of the potential difference between the first potential and the second potential. It is characterized by being set.
[0010]
In the crystal oscillation circuits of the inventions (1) and (2) , when a voltage is applied to the signal inverting amplifier, the excitation drive of the crystal resonator is started. The output of the signal inverting amplifier is subjected to feedback input after phase inversion by a feedback circuit. The feedback input signal is inverted and amplified by the signal inverting amplifier, and is output repeatedly.
[0011]
At this time, the first and second semiconductor switching elements constituting the signal inverting amplifier are turned on and off at different timings by the feedback input, and drive the crystal resonator.
[0012]
In the present invention, the sum of the absolute values of the threshold voltages of the first and second semiconductor switching elements is set to a value equal to or greater than the absolute value of the power supply voltage of the signal inverting amplifier. For this reason, it is possible to avoid the first and second semiconductor switching elements from being simultaneously turned on when the circuit is driven. As a result, it is possible to greatly limit the short-circuit current flowing through the signal inverting amplifier and reduce power consumption. it can.
[0013]
In particular, according to the inventions of (1) and (2) , the first and second transistors can be manufactured so as to satisfy the threshold voltage condition, thereby taking measures against short-circuit current. This eliminates the need for special circuit components for short-circuit current countermeasures. As a result, it is possible to reduce the power consumption of the crystal oscillation circuit without reducing the degree of integration of the entire circuit.
[0014]
In the inventions of (1) and (2) , the absolute value of the threshold voltage of the first and second semiconductor switching elements must be set to a value lower than the absolute value of the power supply voltage of the signal inverting amplifier. There is.
[0015]
(3) The present invention
A bias circuit for applying a first DC bias voltage and a second DC bias voltage to the gates of the first semiconductor switching element and the second semiconductor switching element constituting the signal inverting amplifier;
The first DC bias voltage and the second DC bias voltage are:
Feedback of the signal inverting amplifier input to each gate of the first semiconductor switching element and the second semiconductor switching element to a value where the first semiconductor switching element and the second semiconductor switching element do not have a common ON period. The input DC potential is individually shifted.
[0016]
(4) The present invention
A signal inverting amplifier;
A feedback circuit that has a crystal resonator connected between the output side and the input side of the signal inverting amplifier, inverts the phase of the output signal of the signal inverting amplifier, and inputs the feedback to the signal inverting amplifier;
A bias circuit for applying a DC bias voltage to the signal inverting amplifier;
Including
The signal inverting amplifier is:
A first circuit including a first semiconductor switching element connected to a first potential side and driven to be turned on / off by the feedback input inputted to the gate to drive the crystal resonator;
A second potential connected to a second potential different from the first potential, and driven on and off at a timing different from that of the first semiconductor switching element by the feedback input inputted to the gate to drive and drive the crystal resonator A second circuit including a semiconductor switching element;
Including
The bias circuit includes:
A first bias circuit for applying a first DC bias voltage to the gate of the first semiconductor switching element constituting the signal inverting amplifier;
A second bias circuit for applying a second DC bias voltage to the gate of the second semiconductor switching element constituting the signal inverting amplifier,
The first DC bias voltage and the second DC bias voltage are:
The signal inverting amplifier input to the gates of the first semiconductor switching element and the second semiconductor switching element at a value such that the first semiconductor switching element and the second semiconductor switching element do not have a common ON period. The DC potential of the feedback input is individually shifted.
[0017]
According to the inventions of (3) and (4) , the first and second DC bias voltages are applied to the gates of the first and second semiconductor switching elements constituting the signal inverting amplifier, respectively.
[0018]
The first DC bias voltage and the second DC bias voltage are set such that the first semiconductor switching element and the second semiconductor switching element do not have a common ON period. The DC potential of the feedback input of the signal inverting amplifier input to each gate of the semiconductor switching element is individually shifted.
[0019]
By adopting the above configuration, according to the present invention, the first and second semiconductor switching elements constituting the signal inverting amplifier are turned on and off at different timings by the feedback input, and the crystal resonator is excited. During driving, a common on-period in which both the first and second semiconductor switching elements are turned on does not occur. Therefore, it is possible to obtain a crystal oscillation circuit that can significantly reduce the short-circuit current flowing through the signal inverting amplifier and can stably oscillate with low power consumption.
[0020]
In particular, according to the inventions of (3) and (4) , even when the absolute values of the threshold voltages of the first and second semiconductor switching elements are small, the short-circuit current of the signal inverting amplifier can be reduced. For this reason, the power supply voltage of the crystal oscillation circuit can be lowered by that amount, and also from this aspect, the power consumption of the oscillation circuit can be reduced.
[0021]
(5) The present invention
In (4) ,
The first DC bias voltage is set to the first potential, and the second DC bias voltage is set to the second potential.
[0022]
According to the present invention, when the DC bias voltage is applied, the DC potential of the feedback input to the gates of the first semiconductor switching element and the second semiconductor switching element is individually changed to the first potential of the power source, 2 is shifted to the potential side. Thereby, it is possible to obtain a crystal oscillation circuit capable of reliably reducing the short-circuit current of the signal inverting amplifier with a simple circuit configuration.
[0023]
(6) The present invention
In any one of (1) to (5) ,
The first and second semiconductor switching elements are:
It is characterized by using field effect transistor elements of different conductivity types.
[0024]
(7) The electronic circuit of the present invention is
(1) to (6) are provided.
[0025]
(8) The semiconductor device of the present invention is
It is characterized by including any one of the oscillation circuits of (1) to (6) or the electronic circuit of (7) .
[0026]
(9) The electronic device of the present invention
It is characterized by including any one of the oscillation circuits of (1) to (6) or the electronic circuit of (7) .
[0027]
By doing so, it is possible to reduce power consumption of portable electronic devices such as mobile phones and portable computer terminals, and to reduce power consumption of built-in batteries and secondary batteries such as batteries. It becomes possible.
[0028]
(10) The watch of the present invention is
It is characterized by including any one of the oscillation circuits of (1) to (6) or the electronic circuit of (7) .
[0029]
By doing so, it is possible to realize a portable watch with low power consumption. As a result, it is possible to reduce the size of the watch as a whole by using a smaller battery, and with the same capacity. When a battery is used, it is possible to extend the life of the battery.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Next, preferred embodiments of the present invention will be described in detail with reference to the drawings.
[0031]
(First embodiment)
FIG. 1 shows a crystal oscillation circuit according to a first embodiment of the present invention. The crystal oscillation circuit of the present embodiment is a crystal oscillation circuit used for a quartz type wristwatch.
[0032]
The crystal oscillation circuit of the present embodiment includes a signal inverting amplifier 30 and a feedback circuit. The feedback circuit includes a crystal resonator 10, a resistor 14, and capacitors 16 and 18 for phase compensation. The feedback circuit 30 inverts the phase of the output VD (t) of the signal inverting amplifier 30 by 180 degrees, and uses this as a gate signal. Feedback is input to the gate of the signal inverting amplifier 30 as VG (t).
[0033]
The signal inverting amplifier 30 is connected to a first potential side and a second potential side lower than the first potential side, and is configured to be driven by power supply by a potential difference between both potentials. Here, the first potential is set to the ground potential VDD, and the second potential is set to the negative power supply potential Vreg supplied from the power supply circuit unit 60.
[0034]
The signal inverting amplifier 30 includes a first circuit 40 and a second circuit 50.
[0035]
The first circuit 40 includes a P-type field effect transistor 42 that functions as a first semiconductor switching element. The source of the transistor 42 is connected to the ground side, and the drain is connected to the output terminal 80 side. The feedback signal VG (t) is applied to its gate.
[0036]
The second circuit 50 includes an N-type field effect transistor 52 that functions as a second semiconductor switching element, and the source of the transistor 52 is connected to the power supply terminal side of the power supply circuit section 60 and is connected to the drain. Is connected to the output terminal 80 side (here, connected to the drain of the transistor 42), and the feedback signal VG (t) is applied to its gate.
[0037]
The transistor 42 is a P-type and enhancement-type field effect transistor, and the transistor 52 is an N-type and enhancement-type transistor. The values of the threshold voltage VTP of the transistor 42 and the threshold voltage VTN of the transistor 52 are the sum of their absolute values as shown in the following equation, and the power supply voltage (this embodiment) is applied to the signal inverting amplifier 30. In the embodiment, since the ground potential VDD is set to 0, the power supply voltage is set to be equal to or greater than the absolute value of Vreg which is a potential difference between the ground potential and the power supply potential.
| Vreg | ■ ≦ | VTP | + | VTN | (2)
Further, the absolute value of the threshold voltage of each of the transistors 42 and 52 is set to be a value lower than the absolute value of the power supply voltage as shown by the following equation.
｜ Vreg ｜ ■ ＞ ｜ VTP ｜
| Vreg | ■> | VTN | (3)
As a result, the crystal oscillation circuit of the present embodiment can greatly reduce the value of the short-circuit current that flows to the signal inverting amplifier 30 when the circuit is driven, and can achieve low power consumption.
[0038]
The reason will be described below.
[0039]
FIG. 2 shows a timing chart of a conventional crystal oscillation circuit, and FIG. 3 shows a timing chart of the crystal oscillation circuit of the present embodiment. The horizontal axis shows the time after the power supply voltage Vreg is applied from the power supply circuit section 60. , The vertical axis represents the feedback input VG (t) to the signal inverting amplifier 30 and the on and off states of the transistors 42 and 52, respectively.
[0040]
As described above, in the conventional crystal oscillation circuit, the threshold voltages of the two transistors 42 and 52 constituting the signal inverting amplifier 30 are set so as to satisfy the expression (1). In this case, the relationship between the threshold voltage of each of the transistors 42 and 52, the ground potential VDD, and the power supply potential Vreg is illustrated in FIG. That is, the value of the feedback input VG (t) to the signal inverting amplifier 30 is equal to the potentials of both the threshold voltages VTP and VTN.
VTP> VG (t)> VTN
When a value in the range is taken, there exists a short region in which both transistors 42 and 52 are both turned on.
[0041]
Therefore, as shown in FIG. 2, a common on-period in which both transistors 42 and 52 are both turned on while the transistors 42 and 52 are alternately turned on and off by the feedback signal VG (t) is periodic. And a short current flows from the high potential (VDD) to the low potential (Vreg), which hinders reduction in power consumption.
[0042]
On the other hand, in the present embodiment, the threshold voltages of the transistors 42 and 52 are set so as to satisfy the expressions (2) and (3). FIG. 5 shows the relationship between the threshold voltages, the ground potential VDD, and the power supply potential Vreg in this case. That is, the value of the feedback input VG (t) to the signal inverting amplifier 30 is VTN> VG (t)> VTP with respect to the potentials of the threshold voltages VTP and VTN.
When the value in the range is taken, both the transistors 42 and 52 are surely turned off, and there is no common on-period in which both the transistors 42 and 52 are turned on as in the prior art.
[0043]
That is, as shown in FIG. 3, there is no period during which both transistors 42 and 52 are turned on while the transistors 42 and 52 are alternately turned on and off by the feedback signal VG (t). Therefore, the short-circuit current that has been reduced can be greatly reduced, and the power consumption of the crystal oscillation circuit can be reduced.
[0044]
In particular, in the present embodiment, it is possible to take measures against a short current of the signal inverting amplifier 30 without increasing the number of circuit components.
[0045]
In the present embodiment, the absolute value of the threshold voltage of each of the transistors 42 and 52 is set to a value smaller than the absolute value of the power supply voltage Vreg as shown in the equation (3). Thereby, low power consumption can be realized while maintaining a stable oscillation operation of the crystal oscillation circuit.
[0046]
That is, in the crystal oscillation circuit, the absolute value of the amplitude of the feedback signal VG (t) of the signal inverting amplifier 30 does not exceed the absolute value of the power supply voltage Vreg of the signal inverting amplifier. Therefore, by setting the absolute value of the threshold voltage of each of the transistors 42 and 52 so as to satisfy the above expression (3), the transistors 42 and 52 can be stably and alternately driven on and off.
[0047]
According to the experiments by the present inventors, when the oscillation circuit is driven using the power supply voltage Vreg having an absolute value of 0.9 volts, the sum of the absolute values of the threshold voltages of the transistors 42 and 52 is expressed by the following equation. It was confirmed that a favorable oscillation state can be maintained even when the range is changed, and that power consumption can be reduced.
[0048]
1.4 volts> | VTP | + | VTN |> 0.9 volts Further, in this embodiment, the off-leakage current of the transistors 42 and 52 can be reduced for the following reason. Electric power can be reduced.
[0049]
FIG. 6 is a characteristic diagram showing the relationship between the drain current ID and the gate-source voltage VGS of the enhancement type transistor. As shown in the figure, in the enhancement-type transistor, the ID-VGS characteristic curve shifts to the left as the threshold voltage is lowered, and the off-leakage current increases as shown by the broken line in the figure (in the figure). When VGS is equal to or lower than the threshold voltage VTH and the transistor is turned off, the current ID flowing through this transistor becomes an off-leakage current as shown by a broken line in the figure).
[0050]
Therefore, when the threshold voltage of the transistors 42 and 52 is set low as in the conventional oscillation circuit, the off-leak current below the threshold voltage increases, and the power consumption increases accordingly.
[0051]
In contrast, in the present embodiment, the threshold voltage of each of the transistors 42 and 52 is set to a large value as shown by the equation (2), so that the value of the off-leakage current flowing through each of the transistors 42 and 52 is greatly increased. The power consumption of the entire circuit can be reduced.
[0052]
(Second Embodiment)
In the first embodiment, the case where the threshold voltages of the transistors 42 and 52 are configured so as to satisfy the equation (2) and the short-circuit current is reduced has been described as an example. In the embodiment, even when each of the transistors 42 and 52 is formed under the condition shown in the equation (1) as in the prior art, the first bias voltage is applied to the gate of each of the transistors 42 and 52, so that the first Similar to the embodiment, the short circuit current of the signal inverting amplifier 30 can be reduced.
[0053]
FIG. 7 shows a crystal oscillation circuit of the present embodiment, and FIG. 8 shows a timing chart thereof.
[0054]
The crystal oscillation circuit according to the present embodiment includes a first bias circuit 70 that individually shifts the DC potential of the feedback input VG (t) of the signal inverting amplifier 30 that is input to the gates of the transistors 42 and 52. A second bias circuit 80 is included.
[0055]
Each of the bias circuits 70 and 80 includes capacitors 72 and 82 for removing a DC component, and resistors 74 and 84 for applying a DC bias voltage.
[0056]
The capacitors 72 and 82 are used to remove a direct current component from the gate signal VG (t) and apply the signal to the gates of the corresponding transistors 42 and 52.
[0057]
The resistor 74 is connected between the gate of the transistor 42 and the ground VDD, and raises the DC potential of the feedback input VG (t) input to the gate of the transistor 42 to the ground potential VDD.
[0058]
The resistor 84 is connected between the gate of the transistor 52 and the power supply Vreg, and lowers the DC potential of the feedback input VG (t) input to the gate of the transistor 52 to the power supply potential Vreg.
[0059]
With the above configuration, the gate signal VG (t) fed back to the signal inverting amplifier 30 is converted to VGP (t) and VGN (t) by the first and second bias circuits 70 and 80. As shown, the DC potential is changed to VDD and the power supply potential Vreg, and is applied to the gates of the transistors 42 and 52.
[0060]
Therefore, there is no period during which both transistors 42 and 52 are both turned on while the transistors 42 and 52 are alternately turned on and off. As a result, as in the first embodiment, the signal It is possible to greatly reduce the short-circuit current flowing through the inverting amplifier 30 and reduce the power consumption.
[0061]
In particular, in the present embodiment, the short-circuit current can be reduced even if the absolute values of the threshold voltages of the enhancement type transistors 42 and 52 are small. As a result, the power supply voltage applied to the signal inverting amplifier 30 is reduced, and it is possible to reduce power consumption also from this aspect.
[0062]
The bias voltages applied by the first bias circuit 70 and the second bias circuit 80 are set to potentials other than those in the above embodiments on condition that the transistors 42 and 52 do not have a common on-period. The DC potential of the feedback input to the gates of the transistors 42 and 52 may be individually shifted.
[0063]
The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the gist of the present invention.
[0064]
For example, in the above-described embodiment, the case where the first circuit 40 and the second circuit 50 configuring the signal inverting amplifier 30 are each configured by using one transistor has been described as an example. It is also possible to configure a circuit by combining circuit elements other than those described above without impairing the functions of the first and second circuits 40 and 50.
[0065]
In addition, the semiconductor device including the crystal oscillation circuit and the electronic circuit of the above embodiment is configured, and this is used as a portable phone having a limited power supply capacity, such as a portable telephone, a portable computer terminal, and other portable devices. It is preferable to be mounted on electronic equipment.
[0066]
Further, in this embodiment, the case where the crystal oscillation circuit is used for an electronic circuit for a watch has been described as an example. However, the present invention is not limited to this, and the present invention is not limited thereto, for example, a portable telephone, a portable telephone The present invention is also extremely effective when widely used in portable electronic devices with limited power supply capacity such as computer terminals and other portable devices.
[0067]
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a first embodiment of a crystal oscillation circuit according to the present invention.
FIG. 2 is a timing chart of a conventional circuit.
FIG. 3 is a timing chart of the circuit shown in FIG.
FIG. 4 is an explanatory diagram showing a relationship between a threshold voltage, a power supply potential, and a ground potential of a conventional circuit.
FIG. 5 is an explanatory diagram illustrating a relationship between a threshold voltage, a power supply potential, and a ground potential in the first embodiment.
FIG. 6 is a VGS-ID characteristic diagram of an enhancement type transistor.
FIG. 7 is a circuit diagram of a second embodiment of the crystal oscillation circuit of the present invention.
FIG. 8 is a timing chart of the second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Crystal oscillator 14 Feedback resistance 30 Signal inversion amplifier 40 1st circuit 42 Field effect transistor 50 2nd circuit 52 Field effect transistor 60 Power supply circuit part 70, 80 1st, 2nd bias circuit

Claims (7)

A signal inverting amplifier;
A feedback circuit that has a crystal resonator connected between the output side and the input side of the signal inverting amplifier, inverts the phase of the output signal of the signal inverting amplifier, and inputs the feedback to the signal inverting amplifier;
Including
In a state where the crystal resonator performs stable vibration,
The sum of the absolute values of the threshold voltages of the first semiconductor switching element and the second semiconductor switching element constituting the signal inverting amplifier is set to a value equal to or larger than the absolute value of the power supply voltage of the signal inverting amplifier, and the signal While limiting the short-circuit current that flows to the inverting amplifier ,
An oscillation circuit, characterized in that the absolute values of the threshold voltages of the first and second semiconductor switching elements are each set to be lower than the absolute value of the power supply voltage . A signal inverting amplifier;
A feedback circuit that has a crystal resonator connected between the output side and the input side of the signal inverting amplifier, inverts the phase of the output signal of the signal inverting amplifier, and inputs the feedback to the signal inverting amplifier;
Including
The signal inverting amplifier is:
A first circuit including a first semiconductor switching element connected to a first potential side and driven to be turned on / off by the feedback input to drive the crystal resonator;
A second semiconductor switching element connected to a second potential side different from the first potential and driven on and off at a timing different from that of the first semiconductor switching element by the feedback input to excite the crystal resonator; A second circuit;
Including
In a state where the crystal resonator performs stable vibration,
The sum of the absolute values of the threshold voltages of the first semiconductor switching element and the second semiconductor switching element constituting the signal inverting amplifier is equal to or greater than the absolute value of the potential difference between the first potential and the second potential. set Rutotomoni,
The absolute value of the threshold voltage of the first and second semiconductor switching elements is set to be a value lower than the absolute value of the potential difference between the first and second potentials, respectively. circuit. In any one of Claims 1, 2.
The first and second semiconductor switching elements are:
An oscillation circuit comprising field effect transistor elements of different conductivity types . Electronic circuit comprising the one of the oscillation circuit according to claim 1 to 3. Wherein a is configured to include either the oscillation circuit or electronic circuit of claim 4 according to claim 1-3. An electronic apparatus characterized in that it is configured to include either the oscillation circuit or electronic circuit of claim 4 according to claim 1-3. Watch characterized in that it is configured to include either the oscillation circuit or electronic circuit of claim 4 according to claim 1-3.

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